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Tuesday, March 06, 2012

Less and more

On paper, Gold- and Greenfinch both have a similar post-juvenile moult: "partial". But it's variable, with some birds of both species moulting just the (secondary) coverts while some go as far as to moult primaries, secondaries and some primary coverts; there's a whole range of variation in between.

Here are two birds from this morning demonstrating close to either end of the variation:

This 2cy female Greenfinch is at the lower end of the scale having undergone a rather limited post-juvenule moult; it's retained seven juvenile greater coverts along with all the other 'large' wing feathers.

In contrast, this 2cy Goldfinch has undergone a rather extensive post-juvenile moult having eccentrically moulted two primaries (p5 & 6) — but not the corresponding primary coverts.